RE: link list returned from service program -- RPG400-L

Encapsulation is a good thing.

Indeed. As a general rule, return a pointer to the program to the structure
which is managed by the service program itself (i.e. allocated and destroyed).
The program only knows about the pointer, it knows nothing about the internal
structure. Then pass this pointer as the first argument to procedures
"GetNextCustomer", "GetParentCustomer". And if you put all the code like this
that belongs to the Customer entity into one well-named serviceprogram then
we even have a bit of OO here.

Subject: RE: link list returned from service program
Date: Wed, 12 Mar 2008 08:17:19 -0400
From: WiltC@xxxxxxxxxx
To: rpg400-l@xxxxxxxxxxxx

Actually, I take back what I said a minute ago about your idea being reasonable.

Is there any reason for actually passing back the linked list?

You could easily keep the link list implementation hidden, and just expose procedures like
GetNextCustomer(), GetParentCustomer() that would allow the callers of the service program access to
the data while hiding the fact you're using a linked list.

Encapsulation is a good thing.

Charles Wilt
Software Engineer
CINTAS Corporation - IT 92B
513.701.1307

wiltc@xxxxxxxxxx

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Lim Hock-Chai
Sent: Tuesday, March 11, 2008 6:00 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: link list returned from service program

To create customer family tree. Our customer master file has customer
number field and parent customer number field. Every now and then, we
need to know all the descendants of a customer number. So..., I created
a export procedure that accept a customer number as a parameter. It
will return the caller a link list that represent the customer's family
tree.

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Alan Campin
Sent: Tuesday, March 11, 2008 4:48 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: link list returned from service program

Lim Hock-Chai wrote:

I'm just curious to know if I've an export procedure that returns a
link list to the caller, how safe is it to continue to use the link
list after the service program is destroyed from the activation group?

I have to ask. Why are you returning a linked list from a service
program?

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